Process for producing fluoroalkyl iodide

ABSTRACT

The present invention provides a process for producing a fluoroalkyl iodide represented by the general formula (II):
 
Rf-CH 2 CH 2 I  (II)
 
wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to 20 carbons, the process comprising reacting hydrogen iodide gas with a fluoroalkene in the presence of a catalyst. The present invention also provides a process for producing a fluoroester by reacting the fluoroalkyl iodide with a carboxylate.

TECHNICAL FIELD

The present invention relates to a process for producing a fluoroalkyliodide using a starting material represented by the general formula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons. The present invention also relates to a process forefficiently producing a fluoroester usable as a starting material forwater- and oil-repellents using the production process.

BACKGROUND OF THE INVENTION

In producing a fluoroester usable as a starting material for water- andoil-repellents, represented by the general formula (IV):Rf-CH₂CH₂OCOCX═CH₂  (IV)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons and X is H or CH₃, a process has been proposed whichcomprises reacting a fluoroalkyl iodide with a carboxylate representedby the general formula (III):CH₂═CXCOOK  (III)wherein X is H or CH₃ and K is an alkali metal (Japanese Examined PatentPublication No. 18112/1964). The process, however, generates asby-products a large amount of fluoroalkenes represented by the generalformula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons.

The fluoroalkenes can be used as a starting material for anorgano-fluorosilane represented by the general formula (V):RfCH₂CH₂SiR_(n)X_(3-n)  (V)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons, R is an alkyl or aryl group and n is 0, 1, or 2 (JapaneseUnexamined Patent Publication No. 126621/1975). However, the amount ofthe fluoroalkene required for producing the organo-fluorosilane is toosmall. Accordingly, the production efficiency can be improved if theexcess fluoroalkene is converted into a fluoroalkyl iodide and recycledas a starting material for the above-mentioned fluoroester.

A process (dehydrohalogenation) is known which synthesizes R_(f)-CH═CH₂represented by the above-described general formula (I) from afluoroalkyl iodide (Japanese Unexamined Patent Publication No.69347/1992). However, in the reverse reaction of adding hydrogen iodide(HI) to R_(f)-CH═CH₂, it is known that Rf-CHI—CH₃ is generally obtainedas a main product following Markovnikov rule while a process forefficiently synthesizing Rf-CH₂CH₂I not following Markovnikov rule istotally unknown.

Some reactions of adding hydrogen chloride (HCl) or hydrogen bromide(HBr) to a fluoroolefin have been reported such as a process using AlBr₃as a catalyst (J. Am. Chem. Soc., 72, 3369 (1950)), a process usingCaSO₄/C as a catalyst (J. Am. Chem. Soc., 75, 5618 (1953)), etc.However, the use of hydrogen chloride or hydrogen bromide posesproblems: the reaction rate is extremely low; by-products such aspolymers, etc. are formed. Therefore, such processes cannot be used inindustrial syntheses.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for producinga fluoroalkyl iodide in high efficiency using a starting materialrepresented by the general formula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons.

Another object of the present invention is to provide a process forefficiently producing a fluoroester useful as a starting material forwater- and oil-repellents represented by the general formula (IV) usingthe above-mentioned process:Rf-CH₂CH₂OCOCX═CH₂  (IV)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons and X is H or CH₃.

The inventors carried out intensive research to achieve theabove-mentioned objects. As a result, the inventors found that afluoroalkyl iodide can be produced by reacting a fluoroalkene withhydrogen iodide gas in the presence of a catalyst, and that afluoroester can be efficiently produced using the production process fora fluoroalkyl iodide. The present invention has been accomplished basedon these findings.

More specifically, the present invention relates to the followingtechniques:

Item 1. A process for producing a fluoroalkyl iodide represented by thegeneral formula (II):Rf-CH₂CH₂I  (II)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons, the process comprising reacting hydrogen iodide gas in thepresence of a catalyst with a fluoroalkene represented by the generalformula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons.

Item 2. A process according to Item 1, wherein the catalyst is onemember selected from the group consisting of activated carbon, metalsulfates and a combination of activated carbon and metal sulfate(s).

Item 3. A process according to Item 2, wherein the metal sulfate is oneor more members selected from the group consisting of potassium sulfate,sodium sulfate, calcium sulfate, magnesium sulfate and aluminiumsulfate.

Item 4. A process according to Item 1, wherein the catalyst comprisesone or more Lewis acids.

Item 5. A process according to Item 4, wherein the Lewis acid is one ormore members selected from the group consisting of boron halides,antimony halides, tin halides, titanium halides, zinc halides, aluminumhalides, gallium halides, arsenic halides, iron halides, mercury halidesand zirconium halides.

Item 6. A process for producing fluoroester represented by the generalformula (IV):Rf-CH₂CH₂OCOCX═CH₂  (IV)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons and X is H or CH₃;

the process comprising:

producing a fluoroalkyl iodide represented by the general formula (II):Rf-CH₂CH₂I  (II)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons, by reacting hydrogen iodide gas in the presence of acatalyst with a fluoroalkene represented by the general formula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons; and

reacting the thus produced fluoroalkyl iodide with a carboxylaterepresented by the general formula (III):CH₂═CXCOOK  (III)wherein X is H or CH₃ and K is an alkali metal.

Hereinafter, the present invention will be described in more detail.

According to the invention, a fluoroalkyl iodide is produced by reactinga fluoroalkene with hydrogen iodide gas in the presence of a specificcatalyst.

Examples of the catalyst include (i) a catalyst comprising one or moremembers selected from the group consisting of activated carbon and metalsulfates and (ii) a catalyst comprising one or more Lewis acids.

When a catalyst (i) comprising one or more members selected from thegroup consisting of activated carbon and metal sulfates is used,activated carbon and metal sulfates can be used alone, or in combinationthereof. The activated carbon and metal sulfate(s) are used preferablyin a ratio of 0.1/99.9 to 99.9/0.1 (mass %).

Examples of metal sulfates are potassium sulfate, sodium sulfate,calcium sulfate, magnesium sulfate, aluminium sulfate and the like.

When a catalyst (ii) comprising one or more Lewis acids is used,examples of Lewis acids are boron halides, antimony halides, tinhalides, titanium halides, zinc halides, aluminum halides, galliumhalides, arsenic halides, iron halides, mercury halides, zirconiumhalides and the like.

The process for producing a fluoroalkyl iodide using the above-mentionedcatalyst will be described in greater detail.

According to the process of the invention, a fluoroalkyl iodiderepresented by the general formula (II):Rf-CH₂CH₂I  (II)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons, is produced by reacting in the presence of theabove-mentioned catalyst hydrogen iodide gas with a fluoroalkenerepresented by the general formula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons.

In the compound represented by the above-described general formula (I),a perfluoroalkyl group represented by Rf includes a linear or branchedchain perfluoroalkyl group comprising 1 to 20 carbons. Examples thereofare CF₃, C₂F₅, (n- or iso) C₃F₇, (n-, iso, sec- or tert-) C₄F₉,CF₃(CF₂)_(m) (m is an integer from 4 to 19), (CF₃)₂CF(CF₂)_(i) (i is aninteger from 2 to 17), etc.

Examples of polyfluoroalkyl groups include HCF₂(CF₂)_(p) (p is aninteger from 1 to 19), etc.

The reaction between a fluoroalkene represented by general formula (I)and hydrogen iodide gas can be conducted by a continuous method or abatch method. The reactor for the reaction is not limited; a gas-phasecontinuous reactor equipped with reaction vessel such as fixed bedreactor, fluidized bed reactor, moving bed reactor or a batch reactormay be used.

The process for reacting a halogenated fluorine compound with hydrogeniodide by a gas-phase continuous reaction comprises, for example, thesteps of placing a stainless-steel reaction tube filled with thecatalyst of the invention in an electric furnace, heating the catalystlayer to the reaction temperature, introducing a fluoroalkene into avaporizer at a constant rate using a plunger pump or the like to supplythe vaporized fluoroalkene to the catalyst layer together with hydrogeniodide gas whose flow rate is controlled with a mass flow controller orthe like, or together with hydrogen iodide gas diluted with an inertgas, for inducing a catalytic reaction and recovering the reactionproduct with a subsequent trap or the like. Nitrogen, helium, argon,etc., are preferred as an inert gas for diluting hydrogen iodide gas.Favorable reaction conditions may slightly vary depending on the kind ofthe catalyst used; the reaction temperature is usually within the rangeof about 50 to about 400° C., and preferably about 100 to about 300° C.The reaction can be conducted at atmospheric pressure or at an elevatedpressure. The molar ratio of the fluoroalkene to hydrogen iodide gas ispreferably 1:about 0.2 to about 200. W/F (contact time) may be withinthe range of about 0.1 to about 10 g·sec/ml.

When the reaction is conducted by a batch method, a fluoroalkene,hydrogen iodide gas and a catalyst are placed in an autoclave or likepressure vessel, and the mixture is heated with a heater to the reactiontemperature and left to stand to undergo reaction for a certain periodof time with stirring. Preferable reaction conditions may vary dependingon the kind of a catalyst used; the reaction temperature is usually inthe range of about 50 to about 400° C. and preferably in the range ofabout 100 to about 300° C. The molar ratio of a fluoroalkene to hydrogeniodide gas is preferably in the range of 1:about 0.2 to about 200. Thereaction time may be within the range of about 1 to about 100 hours. Inthe reaction atmosphere, hydrogen iodide gas alone may be used or aninert gas such as nitrogen, helium, argon and the like added to thehydrogen iodide gas.

Hereafter, a process for producing a fluoroester using a fluoroalkyliodide obtained by the above-mentioned production process will bedescribed.

In this process, hydrogen iodide gas and a fluoroalkene represented bygeneral formula (I):Rf-CH═CH₂  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons are reacted in the presence of a catalyst, to give afluoroalkyl iodide represented by general formula (II):Rf-CH₂CH₂I  (II)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons.

Subsequently, the obtained fluoroalkyl iodide is reacted with acarboxylate represented by general formula (III):CH₂═CXCOOK  (III)wherein X is H or CH₃ and K is an alkali metal, to produce a fluoroesterrepresented by general formula (IV):Rf-CH₂CH₂OCOCX═CH₂  (IV)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons and X is H or CH₃.

The reaction of the fluoroalkyl iodide represented by general formula(II) with the alkali metal carboxylate represented by general formula(III) can be performed by generating a mixture with, for example, analcoholic solvent, heating the resultant solution at 125 to 200° C. for1 to 30 hours, and then recovering the ester from the reaction mixture.

Usable as the alkali metal which forms carboxylate are lithium, sodium,potassium, etc. Among these, potassium is particularly preferable.

The reaction can be carried out by a batch method or a continuousmethod. The reactor for this reaction is not limited, and a gas-phasecontinuous reactor equipped with reaction vessel such as fixed bed,fluidized bed, moving bed, etc. may be used, or a batch reactor.

The process for producing a fluoroester using a fluoroalkyl iodideaccording to this invention can achieve the following remarkableeffects:

(1) As compared with the addition of hydrogen chloride or hydrogenbromide, the reaction can be carried out in a shorter period of time,and with less formation of by-products and in high yield;

(2) Fluoroalkene produced as by-products can be used as the startingmaterial for producing fluoroester, which eliminates the necessity ofhaving a separated vessel; and

(3) KI and fluoroalkene generating in the esterification reaction can berecycled as starting materials and therefore production efficiency canbe improved.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below in further detail withreference to Examples and Comparative Examples. However, the scope ofthe invention is not limited to these Examples.

EXAMPLE 1

198 g of CF₃(CF₂)₇CH═CH₂ and 5 g of AlI₃ were charged into a 200-mlstainless-steel autoclave and displacement of the atmosphere withnitrogen was repeated 5 times by vacuum evacuation and charging withnitrogen gas while cooling the autoclave with dry ice/acetone. Theoxygen concentration inside the system was not more than 1 ppm and themoisture content was not more than 1 ppm. Thereafter, nitrogen wasremoved by evacuation and 11 g of hydrogen iodide gas was chargedtherein. Heating was carried out with stirring for two hours at 130° C.After cooling, the liquid in the autoclave was sampled, and GC analysis(gas chromatography analysis) and GC/MS analysis (gaschromatography/mass analysis) were performed. CF₃(CF₂)₇CH₂CH₂I wasproduced at a conversion rate of 2% and at a selectivity of 100%.

EXAMPLE 2

The same process as in Example 1 was conducted except that 41 g ofCF₃(CF₂)₇CH═CH₂, 12 g of CaSO₄/C (25/75 mass %) instead of AlI₃, and 12g of hydrogen iodide gas were used. CF₃(CF₂)₇CH₂CH₂I was produced at aconversion rate of 60% and at a selectivity of 100%.

EXAMPLE 3

The same process as in Example 1 was conducted except that 41 g ofCF₃(CF₂)₇CH═CH₂, 12 g of activated carbon instead of AlI₃, and 12 g ofhydrogen iodide gas were used. CF₃(CF₂)₇CH₂CH₂I was produced at aconversion rate of 20% and at a selectivity of 100%.

EXAMPLE 4

The same process as in Example 1 was conducted except that 41 g ofCF₃(CF₂)₇CH═CH₂, 12 g of CaSO₄ instead of AlI₃, and 12 g of hydrogeniodide gas were used. CF₃(CF₂)₇CH₂CH₂I was produced at a conversion rateof 1% and at a selectivity of 100%.

EXAMPLE 5

The same process as in Example 1 was conducted except that 41 g ofCF₃(CF₂)₇CH═CH₂, 12 g of CaSO₄/C (25/75 mass %) instead of AlI₃, and 24g of hydrogen iodide gas were used. CF₃(CF₂)₇CH₂CH₂I was produced at aconversion rate of 90% and at a selectivity of 100%.

EXAMPLE 6

The catalyst was separated from the reaction liquid obtained in Example5 by filtration, and the unreacted olefin was removed with anevaporator, giving 47.5 g of solid CF₃(CF₂)₇CH₂CH₂I. A 200-ml SUSautoclave was charged with 47.5 g (0.082 mol) of the obtained solidCF₃(CF₂)₇CH₂CH₂I, 9.9 g (0.090 mol) of potassium acrylate, 25 g oft-butanol (solvent), 0.6 g of hydroquinone (polymerization inhibitor)and 0.01 g of hydroquinone monomethyl ether (polymerization inhibitor),and a reaction was then carried out with stirring at 180° C. for 6hours. As a result, CF₃(CF₂)₇CH₂CH₂OCOCH═CH₂ was obtained at aCF₃(CF₂)₇CH₂CH₂I conversion rate of 99% and at a selectivity of 88%. Theresults of NMR analysis revealed that polymerization ofCF₃(CF₂)₇CH₂CH₂OCOCH═CH₂ was not detected.

COMPARATIVE EXAMPLE 1

637 g of CF₃(CF₂)₇CH═CH₂ was charged into a 200-ml quartz vessel and theinterior of the system was then purged with N₂, resulting in oxygenconcentration of 8 ppm. The vessel was UV irradiated with a highpressure mercury-vapor lamp (100W, manufactured by SEN LIGHTSCORPORATION, HL100CH-5-type) while introducing (bubbling) HI into thevessel, and the reaction was conducted for 1 hour. The amount of HIintroduced was 22.4 g. The liquid in the vessel was sampled, and GCanalysis (gas chromatography analysis) and GC/MS analysis (gaschromatography/mass analysis) were carried out. As a result, aconversion rate was 2%, a CF₃(CF₂)₇CH₂CH₂I selectivity was 25% and aCF₃(CF₂)₇CHICH₃ selectivity was 75%.

COMPARATIVE EXAMPLE 2

The same process as in Example 1 was conducted except that 41 g ofCF₃(CF₂)₇CH═CH₂, 12 g of CaSO₄/C (25/75 mass %) instead of AlI₃, and 3.4g of hydrogen chloride gas instead of 11 g of hydrogen iodide gas wereused. CF₃(CF₂)₇CH₂CH₂Cl was produced at a conversion rate of 1.7% and ata selectivity of 100%.

COMPARATIVE EXAMPLE 3

The catalyst was separated from the reaction liquid obtained inComparative Example 2 by filtration, and the unreacted olefin wasremoved with an evaporator, giving 0.9 g of liquid CF₃(CF₂)₇CH₂CH₂Cl.This process was repeatedly conducted. Thereafter, a 200-ml SUSautoclave was charged with 39.5 g (0.082 mol) of the obtained liquidCF₃(CF₂)₇CH₂CH₂Cl, 9.9 g (0.090 mol) of potassium acrylate, 25 g oft-butanol (solvent), 0.6 g of hydroquinone (polymerization inhibitor)and 0.01 g of hydroquinone monomethyl ether (polymerization inhibitor),and a reaction was then conducted with stirring at 180° C. for 6 hours.As a result, CF₃(CF₂)₇CH₂CH₂OCOCH═CH₂ was obtained at aCF₃(CF₂)₇CH₂CH₂Cl conversion rate of 12% and at a selectivity of 80%.The results of NMR analysis revealed that a polymer generated bypolymerization of CF₃(CF₂)₇CH₂CH₂OCOCH═CH₂ was produced at a selectivityof 5%.

INDUSTRIAL APPLICABILITY

The present invention provides a production process for producing, inhigh yield, a fluoroalkyl iodide represented by the general formula(II):Rf-CH₂CH₂I  (II)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to20 carbons, by reacting a fluoroalkene with hydrogen iodide gas in thepresence of a catalyst.

Moreover, according to the present invention, a fluoroester usable as astarting material for water- and oil-repellents can be produced in ashorter period of time and with less formation of by-products byapplying the above-mentioned production process for the fluoroalkyliodide. Additionally, fluoroalkene can be recycled as the startingmaterial and therefore production efficiency can be improved.

1. A process for producing a fluoroalkyl iodide represented by thegeneral formula (II):Rf-CH₂CH₂I  (ii) wherein Rf is a perfluoroalkyl or polyfluoroalkyl groupcomprising 1 to 20 carbons, the process comprising reacting hydrogeniodide gas in the presence of a catalyst with a fluoroalkene representedby the general formula (I):Rf-CH═CH₂  (I) wherein Rf is a perfluoroalkyl or polyfluoroalkyl groupcomprising 1 to 20 carbons.
 2. A process according to claim 1, whereinthe catalyst is one member selected from the group consisting ofactivated carbon, metal sulfates and a combination of activated carbonand metal sulfate(s).
 3. A process according to claim 2, wherein themetal sulfate is one or more members selected from the group consistingof potassium sulfate, sodium sulfate, calcium sulfate, magnesium sulfateand aluminium sulfate.
 4. A process according to claim 1, wherein thecatalyst comprises one or more Lewis acids.
 5. A process according toclaim 4, wherein the Lewis acid is one or more members selected from thegroup consisting of boron halides, antimony halides, tin halides,titanium halides, zinc halides, aluminum halides, gallium halides,arsenic halides, iron halides, mercury halides and zirconium halides. 6.A process for producing fluoroester represented by the formula (IV):Rf-CH₂CH₂OCOCX═CH₂  (IV) wherein Rf is a perfluoroalkyl orpolyfluoroalkyl group comprising 1 to 20 carbons and X is H or CH₃; theprocess comprising: producing a fluoroalkyl iodide represented by thegeneral formula (II):Rf-CH₂CH₂I  (II) wherein Rf is a perfluoroalkyl or polyfluoroalkyl groupcomprising 1 to 20 carbons, by reacting hydrogen iodide gas in thepresence of a catalyst with a fluoroalkene represented by the generalformula (I):Rf-CH═CH₂  (I) wherein Rf is a perfluoroalkyl or polyfluoroalkyl groupcomprising 1 to 20 carbons; and reacting the thus produced fluoroalkyliodide with a carboxylate represented by the general formula (III):CH₂═CXCOOK  (III) wherein X is H or CH₃ and K is an alkali metal.